Pluto's Planethood Will Be Decided Shortly

[Fraser]

Pluto has been considered a planet since its discovery, but this position has come under threat with the discovery of 2003 UB313 (aka Xena), an object larger than Pluto orbiting out further in the Solar System. The International Astronomical Union will be meeting in August to decide on the fate of Pluto. By September, we could have 8 or 10 planets in the Solar System, but there won't be 9 any more.

Read the full blog entry

[parallaxicality]

One possible resolution to the debate is for new categories of planet to be introduced. Mercury, Venus, the Earth and Mars would be “rocky planets”. The gas-giants Jupiter, Saturn, Uranus and Neptune would be a second category.

I've never understood the purpose of this definition; isn't it what we do already?

[homo_cosmosicus]

The International Astronomical Union will be meeting in August to decide on the fate of Pluto. By September, we could have 8 or 10 planets in the Solar System, but there won't be 9 any more.

Pluto is just a big Kuiper belt object, and thats it.
Object with such a low mass, odd orbit, with such big moon
can be only a Kuiper belt object and nothing else.

The history is repeating itself - some of the asteroids originaly
were declared as a planets, but now they are in the group
they belong to - asteroids.

[bsalessi]

Pluto is just a big Kuiper belt object,

That's what I think too. And not only Pluto+Charon but also 2003UB313 (Xena) and the smaller planetoids Brown et al have discovered.
Of course their smallness (when compared to earth and the other planets) don't imply that they aren't worth of interest! To cite one example, 2003EL61 is possibly among the most interesting and bizarre objects in the solar system.

Object with such a low mass, odd orbit, with such big moon
can be only a Kuiper belt object and nothing else.

I do not aggree with this idea. A very low mass certainly dismisses one object as a bona-fied planet but certainly not an odd orbit (excentric? inclined?) or the presence of a big moon.

We have lots of planets with odd orbits among those astronomers have discovered around nearby stars (e.g. Gliese 876b, c, d).

Also, I can imagine the existence of binary planets or planets with very, very big moons. Why not? we have binary asteroids (even ternary or multiple, e.g. Sylvia), binary KBOs, binary stars, binary brown dwarfs, binary galaxies, binary black holes, pulsars and may be even quasars....

The history is repeating itself - some of the asteroids originaly
were declared as a planets, but now they are in the group
they belong to - asteroids.

Well said, but I'd like to add that although they're more like asteroids or planetoids, objects like Pluto, Xena or even Ceres are very diferent to those like Toutatis, Eros or Icarus.

[MrClean]

Pluto will ALWAYS be a planet to us great, unwashed masses regardless of what you say. If you change it they will always name the nine planets then there will be rumblings about how Pluto changed and discussions on why those crazy astornomers changed things, NOT about the fact that Pluto isn't a planet anymore. My wife can't tell you anything about Ceres or any Keiper bult objects, but Pluto and the rest of the Nine she knows.

You can't go back in time, you can only realize your mistakes, go forth and sin no more. Some famous guy said that, I can't quite put my tongue on his name though.

[strangledgoose]

What a delightfull Christmas gift a new planet would be.

[jseefcoot]

I don't think that Pluto, its satellites, or any other such objects should be classified as planets. However, until New Horizons reaches Pluto, we won't know with much certainty exactly how they should be classified, either. I'm willing to bet that we will end up needing a third class of celestial body, if not more. We have small rocky ones, some big gaseous ones, a collection of rocky rubble separating the two, and waaaay out beyond any of these we have the smaller, icy bodies. No way can two or three terms completely classify and describe these thousands (millions?) of objects.

However, think back to taxonomy, the system by which we name animals. It is adaptable and has evolved a little since its inception. A similar method of classification might do more than provide the astronomical world with an enduring system by which we identify things; it could very well help to stifle, in time, some of the head-butting we see on an indivdual and personal level.

While I agree that we do need a definition, something that we can use to draw a line in the sand (so to speak), I think that the timing is perhaps a little premature. We have a mission and it is on the way to the area of our solar system that is responsible for resurrecting this debate once again. That one mission will provide us with more scientific knowledge than all of our efforts to date combined. Sure, it's nearly a decade from arrival, but we've been waiting for several decades already to settle this issue. Why make a decision now, when we don't have all of the facts? I for one am willing to wait a while and hope to be able to settle it once and for all, rather than doing something now and then having to redo it in another decade.

I don't think I have enough education and knowledge to even make a guess as to how objects should actually be classified. I do think that defining the word planet too loosely will create much more confusion than it will ever prevent -- such as the proposed definition that allows anything with sufficient mass to become round under its own gravity. This could result in more planets than there are people on the Earth, if some of the more optimistic estimations of the population of the Kuiper Belt are right. I just think we should know more before we decide.

[homo_cosmosicus]

I do not aggree with this idea. A very low mass certainly dismisses one object as a bona-fied planet but certainly not an odd orbit (excentric? inclined?) or the presence of a big moon.

Salessi, its not only about odd orbit...
Its about tilting, size, orbit, mass, similarity with other Kuiper belt objects...

We have lots of planets with odd orbits among those astronomers have discovered around nearby stars (e.g. Gliese 876b, c, d).

Also, I can imagine the existence of binary planets or planets with very, very big moons. Why not? we have binary asteroids (even ternary or multiple, e.g. Sylvia), binary KBOs, binary stars, binary brown dwarfs, binary galaxies, binary black holes, pulsars and may be even quasars....

Very interesting idea, you mention extrasolar planets... its really time
to create definion of a "planet".

[homo_cosmosicus]

Pluto will ALWAYS be a planet to us great, unwashed masses regardless of what you say.

Ok, you are "great, unwashed", and we are "small minded", "brainwashed"...

Being "small minded, brainwashed" I want to give you short IQ test:

There are 9 animals:

1-st, small, animal walks on 4 legs, eats grass, has one stomach with 4 comparments, and produces milk.
2-nd, small, animal walks on 4 legs, eats grass, has one stomach with 4 comparments, and produces milk.
3-th, small, animal walks on 4 legs, eats grass, has one stomach with 4 comparments, and produces milk.
4-th, small, animal walks on 4 legs, eats grass, has one stomach with 4 comparments, and produces milk.
5-th, big, animal walks on 4 legs, eats grass, has one stomach with 4 comparments, and produces milk.
6-th, big, animal walks on 4 legs, eats grass, has one stomach with 4 comparments, and produces milk.
7-th, big, animal walks on 4 legs, eats grass, has one stomach with 4 comparments, and produces milk.
8-th, big, animal walks on 4 legs, eats grass, has one stomach with 4 comparments, and produces milk.
9-th animal is legless, coldbladed, eats small birds, insects, eggs, produces venom.


Question:
Which animal doesn't belong to the members of the subfamily Bovinae of the family Bovidae, ie - which animal is not cattle?

[homo_cosmosicus]

I don't think that Pluto, its satellites, or any other such objects should be classified as planets.

I can't wait to see Pluto demoted to Kuiper Belt object - lets name it "Kuperoid", and other such objects - Kuperoids.

[Hadron]

Hello everybody, new here... Perhaps another criteria could be the object's proximity to other objects in or near the orbit. This would eliminate everything in the asteroid belt, and most of everything in the Kuiper belt, unless the object in question is "round". hopefully my 1st post doesn't flag me as an idiot.

[antoniseb]

hopefully my 1st post doesn't flag me as an idiot.

Welcome Hadron. Your first post was just fine. We do have some threads that have been floating around about what criteria might get used for planets. You coud read those. In the end though we should just wait a couple months till the IAU makes their call on the definition.

[aurora]

Pluto will ALWAYS be a planet to us great, unwashed masses regardless of what you say. If you change it they will always name the nine planets then there will be rumblings about how Pluto changed and discussions on why those crazy astornomers changed things, NOT about the fact that Pluto isn't a planet anymore. My wife can't tell you anything about Ceres or any Keiper bult objects, but Pluto and the rest of the Nine she knows.

You can't go back in time, you can only realize your mistakes, go forth and sin no more. Some famous guy said that, I can't quite put my tongue on his name though.

As others have pointed out, at one time Ceres was considered a planet. But that changed.

People are capable of learning new information. Lots of things have been learned in our lifetimes. Classification schemes have been altered to keep pace.

[MrClean]

Ok, you are "great, unwashed", and we are "small minded", "brainwashed"...

Being "small minded, brainwashed" I want to give you short IQ test:

There are 9 animals:

1-st, small, animal walks on 4 legs, eats grass, has one stomach with 4 comparments, and produces milk.
2-nd, small, animal walks on 4 legs, eats grass, has one stomach with 4 comparments, and produces milk.
3-th, small, animal walks on 4 legs, eats grass, has one stomach with 4 comparments, and produces milk.
4-th, small, animal walks on 4 legs, eats grass, has one stomach with 4 comparments, and produces milk.
5-th, big, animal walks on 4 legs, eats grass, has one stomach with 4 comparments, and produces milk.
6-th, big, animal walks on 4 legs, eats grass, has one stomach with 4 comparments, and produces milk.
7-th, big, animal walks on 4 legs, eats grass, has one stomach with 4 comparments, and produces milk.
8-th, big, animal walks on 4 legs, eats grass, has one stomach with 4 comparments, and produces milk.
9-th animal is legless, coldbladed, eats small birds, insects, eggs, produces venom.


Question:
Which animal doesn't belong to the members of the subfamily Bovinae of the family Bovidae, ie - which animal is not cattle?

Funny, I know the answer to this one but all I can think is Jackass.

Hmmmm, must be a message there, ya think?

[MrClean]

As others have pointed out, at one time Ceres was considered a planet. But that changed.

People are capable of learning new information. Lots of things have been learned in our lifetimes. Classification schemes have been altered to keep pace.

Ceres was found and declared a planet in 1801 and reclassified an asteroied in 1802. I wonder what the percentage of the population knew or even cared about the whole event at the time. Show me a gradeschool textbook for the average Kansas kid in 1801 that Tells about the planet Ceres. Now show me a text from after Pluto's discovery that doesn't list it as a planet.

Sure, NOW we say it isn't a planet and truthfully we've said it probably isn't one for quite some time, but to the general populace it is one and should be grandfathered in.

[parallaxicality]

Actually, Ceres wasn't reclassified until at least 1860. The term "asteroid" was proposed by William Herschel fairly early on but the asteroids were still considered planets well into the 19th century.

The difference between then and now is that the previous controversy was of little interest to anyone outside the Royal Society, while this one is entrenched in wider culture. I suppose you could blame the mass media.

[hhEb09'1]

Which animal doesn't belong to the members of the subfamily Bovinae of the family Bovidae, ie - which animal is not cattle?

There are plenty of animals that belong to Bovinae, but are not cattle.

[Halcyon Dayz]

If you change it they will always name the nine planets then there will be rumblings about how Pluto changed and discussions on why those crazy astronomers changed things, NOT about the fact that Pluto isn't a planet anymore.

So?
Consider it as an opportunity to get the public actually talking about astronomy.

"There is no such thing as bad publicity."

[Nerthus]

Ok, you are "great, unwashed", and we are "small minded", "brainwashed"...

Being "small minded, brainwashed" I want to give you short IQ test:

There are 9 animals:

1-st, small, animal walks on 4 legs, eats grass, has one stomach with 4 comparments, and produces milk.
2-nd, small, animal walks on 4 legs, eats grass, has one stomach with 4 comparments, and produces milk.
3-th, small, animal walks on 4 legs, eats grass, has one stomach with 4 comparments, and produces milk.
4-th, small, animal walks on 4 legs, eats grass, has one stomach with 4 comparments, and produces milk.
5-th, big, animal walks on 4 legs, eats grass, has one stomach with 4 comparments, and produces milk.
6-th, big, animal walks on 4 legs, eats grass, has one stomach with 4 comparments, and produces milk.
7-th, big, animal walks on 4 legs, eats grass, has one stomach with 4 comparments, and produces milk.
8-th, big, animal walks on 4 legs, eats grass, has one stomach with 4 comparments, and produces milk.
9-th animal is legless, coldbladed, eats small birds, insects, eggs, produces venom.


Question:
Which animal doesn't belong to the members of the subfamily Bovinae of the family Bovidae, ie - which animal is not cattle?

So, are you saying that the gas giants and the terrestrial planets have more in common with each other to the diffence of only size, than they do with pluto and the kupier belt objects? From what I've observed the only things the gas giants and the terrestrial planets have in common is enough mass to give them a spherical shape and that they orbit the sun directly on the ecliptic, yet they have totally different compostitons and formation processes. The only big difference the KBOs have with the terrestrial planets are their orbits. Their compositions are different as well, but not to the far extent as the difference between gas giants and terrestrials.

The word planet is extremely unscientific, and is equivalent to the way Aristotle use to classify animals. Flying insects, birds, and bats were all in the same category although they only have one or two similarities with one another, that are big and quite apparent, yet they have much more differences than similarities and still don't have close relation. Today we know that bats are mammals, birds are reptiles, and flying insects are insects, and that they are all animals. We should use this same scientific sense for our celestial bodies. A way to fix this would be something like calling everything orbiting a star directly a planet, from the smallest bit of dust to another star, then further classify things such as terrestrial planets, asteriods, gas giants, KBOs, scattered disc objects, oort cloud objects and comets, and etc..

[parallaxicality]

Personally, I'm of the opinion that gas giants should be reclassified as "minor stars", and their moons as planets. A planet or minor planet would thus be an object composed primarily of elements heavier than hydrogen and helium. The difference, rather than sphericity, which is too vague, would be internal diffrentiation.

[caedmon]

As a layman and a traditionalist, I think that Pluto should keep its status as a 'planet', because people like me understand that. Scientists need to remember that we simple folk need simple words to remember these things.

In scientific circles, use the phrase 'sun-orbiting object' or 'planet-orbiting object', which seem to me to a more specific reference to the subject at hand. Then add in words for things like irregular or regularized shape, eccentric or regular orbit, etc.

*shrug*

If Xenia really is as big as observations claim, I would have no problem calling it the tenth planet.

[aurora]

Ceres was found and declared a planet in 1801 and reclassified an asteroied in 1802.

Cite?

Show me a gradeschool textbook for the average Kansas kid in 1801 that Tells about the planet Ceres.

Kansas became a state in 1861.

[Hull]

If Pluto was concidered an asteroied and not a planet a year ago, do you think we would have sent New Horizons to it?

[parallaxicality]

We're planning to send a probe to Ceres in 2011, so yeah.

[homo_cosmosicus]

So, are you saying that the gas giants and the terrestrial planets have more in common with each other to the diffence of only size, than they do with pluto and the kupier belt objects?

Dear Nerthus, no, I'm not saying that terrestrial and gas planets have that much in common...

you are right, I oversimplyfied the IQ test, but it was just an example, nothing else.

From what I've observed the only things the gas giants and the terrestrial planets have in common is enough mass to give them a spherical shape and that they orbit the sun directly on the ecliptic, yet they have totally different compostitons and formation processes.

Don't you think its not only mass to give them a spherical shape, but also orbit and tilting?

The only big difference the KBOs have with the terrestrial planets are their orbits. Their compositions are different as well, but not to the far extent as the difference between gas giants and terrestrials.

Orbits - yes, but about composition - don't know, lets wait and see. Maybe they are a big dirty snowballs.

[homo_cosmosicus]

So?
Consider it as an opportunity to get the public actually talking about astronomy.

Exactly!

I was only reading this forum, but when I saw, finally, that Pluto's status will be reviewed, I decided to talk about it, and I don't care if somebody thinks I'm a jackass if I consider Pluto just a Kuiper belt object, and not an planet.

For me, personally, it is an insult on human mind and logic to call Pluto "planet".

[homo_cosmosicus]

Ceres was found and declared a planet in 1801 and reclassified an asteroied in 1802.

Wrong... as parallaxicality noted, Ceres's status was reclassified much later...

For details, read:
When Did the Asteroids Become Minor Planets?
http://aa.usno.navy.mil/hilton/Aster...orplanets.html

[hhEb09'1]

For me, personally, it is an insult on human mind and logic to call Pluto "planet".

Pluto's a planet!

[homo_cosmosicus]

If Xenia really is as big as observations claim, I would have no problem calling it the tenth planet.

I would have no problem calling Xenia the tenth planet,
ONLY if other round KBO objects will be given the status of planet,
AND if a handfull of round asteroids will also join the family of planets.

[homo_cosmosicus]

Pluto's a planet!